1. Field of the Invention
The present invention relates to a computer-readable recording medium which records a remote control program used for management of a protected network, to a portable terminal device and to a gateway device. More particularly, the present invention relates to a computer-readable recording medium which records a remote control program for acquiring data within a protected network by external operations. The present invention also relates to a portable terminal device and a gateway device.
2. Description of the Related Art
To devices connected to Internet from a network of houses or offices, direct connection from an external network is restricted for security reasons. This network protected from the outside is hereinafter referred to as a protected network. An access restriction described above is performed through an intermediate function referred to as a firewall or a gateway device (hereinafter, referred to as a gateway device including a firewall). The gateway device is generally set to permit only a minimal access request from the outside.
In reality, however, the following problem arises. Due to this connection restriction, even when a user as an original owner tries connection to the protected network from a device (within a local network different from the protected network) in a visiting place, this connection is restricted as that from the outside. Therefore, the gateway device may be set to allow a user to connect to a device within the protected network also from the outside. The simplest device connection method which can be used is a method for performing a gateway setting such as port mapping setting and for publishing a specific internal device to the outside. However, when this setting is performed, a protection function of the gateway device does not operate at all for the access to the published device. Therefore, the published device is always exposed to devices in the world and as a result, is in danger of being attacked by a malicious third party.
Meanwhile, a portable terminal device carried by a user can be treated as a reliable device previously authenticated by a gateway, in which a secure path can be set using a device authentication function and a communication encryption function such as VPN (Virtual Private Network) function. In a conventional example, there is used a method of using such a secure path to perform communication between internal network devices and peripheral local network devices.
There is disclosed a technology in which when a content published on the Internet by a file server is required, a proxy acquisition server is allowed to acquire the content by the control from a mobile phone (see, e.g., Japanese Unexamined Patent Publication No. 2002-32286).
However, the technology disclosed in Japanese Patent Application Publication Unexamined No. 2002-32286 assumes that the proxy acquisition server can access to the file server. Therefore, this technology cannot be applied to the case where the file server is placed within a LAN protected by a gateway device.
Accordingly, there is considered a method of acquiring a content using a mobile phone connected through the VPN to a LAN at home and transferring the content to a network device in a visiting place. However, the method of thus mediating data communication using a portable terminal device has the following problems.
The first problem is as follows. The portable terminal device must be reduced in weight to allow a user to carry the device. Therefore, the terminal device is limited in its battery capacity as well as limited in its driving time. Further, the portable terminal device increases in its power consumption according to increase in its work rate and data communication amount. Therefore, the terminal device has difficulty in mediating data communication for many hours.
The second problem is as follows. A CPU of the portable terminal device also has problems of weight and power consumption. Due to these problems, a CPU having a relatively low processing speed is frequently used. Due to this low calculating ability, the portable terminal device is also lowered in its data communication speed.
It is basically possible for a user to allow only a network device in a visiting place to perform direct communication with a network device at home. However, a user must considerably change the setting of the gateway device from the outside. Accordingly, it is impractical in terms of trouble for the user to check information of local network devices and to perform change operations in each case.